Present invention relates to a set of pneumatic tires that are mounted on a vehicle such as a compact, subcompact or Kei car or other passenger car, and to an arrangement of mounting the pneumatic tires on such vehicle. The invention especially relates to the set of tires and tire-mounting arrangement, in which tires on drive wheels are shaped as same as tires on non-drive or trailer wheels.
Conventionally, on a typical passenger car such as a compact, subcompact or Kei car, tires that are identical with each other are mounted on wheels of the vehicle and are exchanged with each other in a rotational manner at an adequate timing. For example, at a time an accumulated mileage reaches a predetermined value, swapping of the tires is made between front and rear wheels and between right-hand and left-hand wheels, so as to alleviate variation among extent of wearing of the tires. Timely rotation of the tires would smoothly take away unevenness in amounts of wear and damage of the tires, which would otherwise varied by positions of the wheels.
Thus, most of proposals for reducing the variation of wear, which have been made to date, require the tire rotation as a prerequisite. For example, JP2010-195385A (Japan patent application publication No. 2010-195385) proposes designing of tread pattern so that developing of the wear makes the tread pattern eventually in a right-left symmetry in order to enable the rotation of tires even having non-symmetric tread patterns.
According to a tire proposed in JP1988(S63)-301108A, orientation of tread pattern is opposite between tires mounted on right-hand and left-hand wheels. Nevertheless, as shown in FIG. 1 of JP1988(S63)-301108A, the tire rotation is enabled and seems to be required as a prerequisite.
According to a tire proposed in JP2008-260423A, tires on front wheels are “provided with high friction coefficient to road surface so as to increase accelerating and braking performances” (paragraph 0050); and rear wheels are given with some camber angle as shown in FIG. 4, and tires on the rear wheels are “provided with lower friction coefficient to road surface so as to improve fuel efficiency” (paragraph 0050). In ways to decrease the friction coefficient, it is described as follows: “as a first method, width of the tire is decreased; as a second method, adopted is a tire material having smaller friction coefficient; as a third method, adopted is a tread pattern that decreases friction coefficient of the tread; and as a fourth method, increased is an inner pressure of the tires”. Whereas in the JP2008-260423A, a detailed embodiment is disclosed in respect of manner of controlling the camber angles on course of running of the vehicle, no disclosure is made on how and what extent the camber angles are given and on how to tackle problems related to the tire rotation.
Meanwhile, JP1999(H11)-321237A discloses a pneumatic radial tire that “has higher stiffness in rubber material on a part at outside of a vehicle than that at inside”. This is to cope with a problem that: “center of gravity of a minivan vehicle or of one-box design vehicle is in higher position than that of a sedan vehicle; a large load is applied to the part at outside of the vehicle; and proceeding of wear is more rapid at the outside of the vehicle than at the inside”.